1. Field of the Invention
This invention relates generally to a training and recreation device for enabling the simulation of ski turns on a "dry-land" slope devoid of snow or ice.
The art of skiing on snow has passed through a large number of stages of development. In each stage, the proposer of a new technique would advocate the adoption of that technique as superior to earlier techniques in one or more respects. Perhaps the proposed new technique would enable the skier to cope with more adverse conditions of the ski terrain of snow and ice. Or perhaps the development of a new item of ski equipment has made feasible a new technique which would not have been feasible without the aid of the newly-developed item of equipment. Conversely, proposed new techniques have led to the development and reduction to practice of appropriate items of equipment without which the technique would not have been fully feasible.
As is well known, there have been many different concepts concerning the proper location of the center of gravity of the body of the skier along the line parallel to the longitudinal axis of the skis and several feet above it. At one time, it was universally accepted that the center of gravity of the skier's body should be well forward with respect to the position where the skier's feet rested on the skis. Later, some very successful skiers suggested that the center of gravity of the skier's body might well be positioned aft of the location of the skier's feet on the skis.
Just as there have been numerous concepts concerning the proper location of the center of gravity of the skier's body in a fore-and-aft direction, there have also been numerous theories as to where the center of gravity of the skier's body should be located in a transverse direction, normal to the longitudinal axis of the skis.
In the very highly-developed technique that was taught in the Alps of Europe in the 1950's, a skier "traversing" the slope of a hill or trail in a diagonal direction with respect to the fall line of the hill should be "facing down the fall line" with his shoulders positioned along a line transverse and perpendicular to the fall line. The body of the skier was to be flexed so that the rear side of the skier's midsection would be pointing "uphill," while the center of gravity of the skier's body would be positioned roughly above the "downhill ski" as the traverse maneuver was executed. Under those circumstances, it was important for most of the weight of the skier's body to be borne by the downhill ski.
When the skier approached the point on the slope where he wished to execute a turn, he would bend his knees slightly, and then straighten his legs, whereby the tails of the skis were somewhat "unweighted". With the tails of the skis unweighted, the skier would then thrust his heels in a direction "up the hill" while concurrently shifting his body weight "down the hill". In order for the shift of body weight downhill not to result in a fall by the skier, it was necessary for the thrust of the skier's heels to initiate a turn of the skis, so that the front tips of the skis began to assume a position directly beneath the skier's body in its downwardly-shifted position. As the tips of the skis "came around", thereby bringing about the execution of a smooth turn, the weight of the skier's body was centered forward of his feet but not so far forward as the tips of his skis. Thus, the force transmitted from the forebodies of the skis through the skier's feet and legs to his center of gravity prevented the skier from "falling downhill." As the skier completed his smooth turn, he assumed a new traverse position crossing the slope in the opposite direction, his weight being centered over his downhill ski. Once again, most of his weight was supported by the downhill ski. And further, the skier assumed a new position in which he was still facing downhill with his shoulders positioned along a line perpendicular to the fall line, and in which the backside of his body was again pointing uphill. During the turn, the "uphill ski," before the turn, became the "downhill ski" after the turn. Correspondingly, the downhill ski prior to the turn became the uphill ski after the turn. Prior to the turn, the uphill ski was positioned slightly ahead of the downhill ski. Then, when the skis exchanged identities as between uphill and downhill, the former downhill ski became the new uphill ski and was positioned slightly ahead of the new downhill ski.
Many of the principles of the technique just described remain valid in the techniques that are now being taught in the ski schools of the 1990's. For instance, it is still regarded as important for the center of gravity of the skier's body to be positioned roughly over the "downhill ski" at all times. But the techniques being taught at the present time put more emphasis on the "carving" of a smooth turn than did the European technique described above. The carving of a smooth turn depends upon two particular physical characteristics of the ski. One of those characteristics is the flexibility of the ski about an axis transverse to the ski and passing through the point where the skier's foot rests upon the ski. Another characteristic of the ski which is important in the execution of the current technique is the fact that the width of the forebody of the ski between the skier's foot and the tip of the ski and the width of the afterbody of the ski between the skier's foot and the taft of the ski are both somewhat greater than the width of the ski at the point where the skier's foot rests upon it. Thus, proceeding from the tip toward the taft of the ski, the width of the ski first broadens sharply and then gradually narrows as one approaches the "waist" of the ski where the skier's foot is attached to it by bindings. Then, continuing in an aft direction, the width of the ski broadens again as the taft of the ski is approached. This configuration of the width of the ski might be referred to as "tapering toward the middle."
The flexibility of the ski and the configuration "tapering toward the middle" are the structural characteristics which permit the execution of the ideal "carved" turn. As the turn is executed, the ski, which in rest position and unweighted has a "camber" so that the midpoint of the ski is higher than the forebody and the afterbody, during the carving of the turn temporarily assumes an "inverse camber." The weight and centrifugal force imposed upon the waist of the ski during the turn force the ski into the configuration of an are which is coincident with the desired path of the carved turn in the snow.
Clearly, the foregoing statements are based upon an assumption that the planes of the bottoms of the respective skis are not oriented parallel to the surface of the snow, but are inclined at a sharp angle thereto. Depending upon the stage within the turn, the angle of inclination might be as much as 45.degree., or perhaps even more in a very "tight" turn. Of course, the angle of inclination with respect to the surface of the snow would be less when the turn is being completed than at the stage when the sharpest turning activity is occurring. Again, the nature of the snow terrain would influence the degree of "edging" of the skis with respect to the snow. If the surface of the snow is icy, the skis would in all probability be more drastically edged with respect to the terrain than of the surface were "fluffy powder."
During the foregoing discussion, the importance of maintaining the center of gravity of the skier's body over the downhill ski has been stressed. Moreover, it has been emphasized that the weight of the skier's body should be borne mainly through the foot which rests on the downhill ski. Clearly, the two skis are "differentially weighted" at almost all times. We have not yet referred to any "differential edging" of the two skis with respect to the surface of the terrain.
In the earlier discussion of the prior favored technique, it was mentioned that the tails of the skis were partially unweighted in order to initiate a turn. This unweighting of the skis involved a forward shift of the center of gravity of the skier's body. In the most recently favored technique, there is more emphasis on the shift of the center of gravity of the skier's body in a direction "down the fall line," rather than forward over the skis. As the skier's body weight is shifted "down the fall line," it is clear that the skier must take some action in order to prevent himself from "falling down the fall line." That action is the initiation of the turn which brings about a re-positioning of the tips of the skis in the direction of the turn, so that the skier's weight can be supported by the forebodies of the skis, thereby preventing a fall by the skier. The farther down the fall line the center of gravity of the skier's body is shifted, the more rapidly the skis must execute the "carved turn" in order that the forebodies of the skis may assume a position under the center of gravity of the skier's body so as to support it. The faster and farther the skier's body is shifted in a direction down the fall line, the more rapidly the turn must be executed. Bringing about a more rapid execution of the turn in most instances will involve a sharper edging of the skis, and a dissimilar weighting of the skis in order to impose maximum burden on the ski which is on the outside of the turn being carved. Accordingly, the ski on the inside of the turn, which is to become the "uphill ski" after the completion of the turn, may bear very little of the weight of the skier's body.
When good snow conditions are available, and when a skier is properly equipped, the technique just mentioned can be taught and learned "on the slope." However, when a suitable slope with favorable ski conditions is not available, it becomes important to have access to a training device which can simulate the aforementioned conditions so as to enable the skier to develop and maintain good skiing habits in the practice of the new technique. For instance, if a skier desires to develop, maintain, or refine his skills "between seasons," a "ski simulator" would be very valuable. If such a simulator were available, the "off-season skier" would need only a gently sloping surface of pavement upon which to use his simulator. The factors that the practicing skier must focus on and properly coordinate are: 1) the lateral shift of the center of gravity of his body in a "downhill" direction; 2) the proper coordinated "edging" of his feet to simulate the way in which his skis would be edged during the execution of a turn; and 3) the differential weighting placed upon the two feet in order to simulate the differential weighting of the skis on a snow surface. Once again, a foot which is the "downhill foot" prior to the turn and accordingly bears a disproportionate part of the skier's weight becomes the Uphill foot after the completion of the turn and is relieved from bearing some or all of the skier's weight.
2. Description of the Prior Art
Until now, there has been no available device that satisfactorily simulates the execution of a ski turn "on dry land." The familiar "skateboard" will not suffice, either with or without modifications. Skateboards are designed so that the feet of the user are oriented at least partially transversely upon the body of the skateboard. The user of the skateboard causes the board to turn one way or the other depending upon whether he accentuates the weight placed upon his heels or upon his toes. The linkage of the skateboard is such as to produce a turn thereof when one side of the body of the board is weighted more heavily than the other. The skateboard is designed in such a way that it will turn in a direction toward the side of the board which is more heavily weighted than the other. Clearly, for a skier who needs to learn to weight preferentially his "outside foot," a skateboard is exactly the "wrong way to go."
U.S. Pat. No. 4,235,448-Thomas is entitled "Skiing Simulator," but, like a skateboard, seems to be based upon the wrong assumption concerning the distribution of the weight of the skier. The mechanism of the cited patent is such that the "skateboard-type" platform upon which it is based will turn toward the side thereof that is more heavily weighted. This is directly contrary to the principles set forth in the foregoing paragraphs describing the two techniques, one earlier, and the other, the latest. Moreover, the structure of the Thomas patent is such that the soles of the feet of the user of the Thomas simulator are always in the same plane. As has been made clear in the foregoing paragraphs, the respective feet of a skier executing either of the described techniques on snow terrain are almost always in different planes. Those planes may on occasion be parallel to each other, or need not be parallel, but in any event they are not the same plane. Thus, the apparatus in accordance with the Thomas patent is not an adequate device for the simulation of real skiing conditions or the practice of either of the aforementioned ski techniques. Furthermore, there seems to be no other prior-art device or disclosure which does permit valid simulation of skiing conditions or the practice and development of proper ski technique.